Field of the Invention
The present invention relates to an image data compressing device for an endoscope which is capable of compressing image data in accordance with the characteristic of each of the colors with respect to the color image provided by the endoscope.
In the known type of endoscope for providing color images which utilizes the field sequential color television system, the light of three primary colors such as red, green, and blue is sequentially irradiated onto an object such as an organism, and the reflected light of each of the individual colors is received by an imaging device such as a CCD where it is converted into an electrical signal. After the thus-obtained picture signals are stored in memories in succession, they are converted into color television signals by a processor to be displayed on a color monitor. This type of color endoscope utilizing the field sequential system was proposed, for example, in the specification of U.S. Pat. No. Re. 31290.
Means for digitizing and storing color image signals of a type that can be used in the above-described color endoscope are known. In one example of such means, analog red, green, and blue picture signals provided by an image inputting device for an endoscope of the type shown in FIG. 1 are stored in a digital memory device of the type shown in FIG. 2 and incorporating a data compressing circuit. In this known image inputting device for an endoscope, as shown in FIG. 1, the light illuminated from a lamp 116 is decomposed into the three primary colors of red, green, and blue by a rotary filter 114, and the light of these three primary colors is sequentially made incident upon a light guide 117 so as to be irradiated onto an organism from the forward end of the light guide 117.
Visual image information on the organism is converted by a CCD 101 into electrical signals disposed at the forward end of the inserted portion of an endoscope, and these picture signals are input to an amplifier 102 where they are amplified to a predetermined voltage level. The amplified picture signals then enter a gamma correcting section 103 where they are gamma corrected. After the gamma corrected picture signals have been converted into digital signals by an analog/digital converter 104, they enter a switch-over switch 105 which is changed over by the control singals, and are then sequentially recorded in red, green, and blue image memories 106, 107, and 108. The picture signals contained in the red, green, and blue image memories 106, 107, and 108 are sequentially read out by the control signals from a control signal generating section 112, and are converted into analog signals by corresponding digital/analog converters 109, 110, and 111. Thereafter, the analog picture signals are fed to red, green, and blue picture signal output terminals together with the synchronizing signals from a synchronizing signal generating circuit 113.
Next, the thus-obtained red, green, and blue analog picture signals are input to a digital memory device such as that shown in FIG. 2 through a RGB inputting section 121. After they have been digitized by an analog/digital converter 122, they are compressed by a compressor 123, and are then stored in a digital memory 124. When the data is read out from the memory 124, the digital data stored in the digital memory 124 in a compressed form is first expanded by an expander 125, and is converted into an analog signal by a digital/analog converter 126, which is then fed to a RGB output section 127. This digital memory device also includes a control circuit 128 for supplying control signals to the various sections.
Compressors of a type that can be employed in the above-described digital memory device were proposed, for example, in the specification of Japanese Patent Laid-Open No. 243075/1987. The compressor of this type includes an operating circuit which employs complicated algorithms to compress data, and therefore provides compressed data through very complicated calculations.